On-line advertisements allow advertisers to reach a wide range of audiences through the Internet. The advertisements can be placed at specific areas of specific web pages. For example, a department store may place an advertisement on the home page of an on-line news web site. The advertisements can be associated with specific keywords and appear as sponsored links on search result web pages in response to user query having search terms that match the specific keywords associated with the advertisements. For example, when a user types the keyword “plumbing” into a search engine, the search results web page may include, in addition to the search results, a list of advertisements shown as sponsored links placed at an area of the search results page. The sponsored link may include a title, a short text description of the product or service being advertised, an URL of the advertiser, and a location of the advertiser. Some of the search results can also be advertisements. For example, the search results for the keyword “plumbing” may include web pages of plumbing services. Each search result may include a title, a snippet of the text in the web page, and an URL of the web page.
Advertisers benefit from the advertisements when users click on links associated with the advertisements or otherwise act on the advertisements to purchase products or services being advertised. Whether an advertisement performs well may depend on a number of factors, such as whether the advertisement appears near the top of a search results page so that the users can see the advertisement without having to scroll down several pages. The performance of an advertisement may depend on the quality of the advertisement, such as whether the text description of the advertisement is interesting and provides a positive impression to the user.